You would have to switch out the single quad with a fairly highly tesselated set of billboarded quads. If I were doing it, the approach I'd take is, say, that if the wall were three dimensional, as opposed to just a single 2d quad ( e.g., like a flattened cube ) I'd *fill* it with particles, turn off the wall, and let the particles fall.

Uh... putting on thinking cap... perhaps instead of individual particles, you'd instead massively tesselate the wall, and treat each junction like a point in a verlet integrated system? You'd probably get "jello", but with tuning and damping it might be cool.

If you're going for a somewhat cinematic effect, I'd probably start with my wall texture, and then blend that into a disintegrated texture which somewhat resembles your particle system; that might produce a nice lead-in to the effect. Textured billboarded quads, or point-sprites on an nvidia card would probably work the best for the particles themselves.